The present invention is generally related to an alternating pressure valve system for supplying fluid to an alternating pressure air mattress.
Air mattress systems help prevent xe2x80x9cbed soresxe2x80x9d from developing in patients who are confined to laying on a mattress for long periods of time. The skin xe2x80x9cinterface pressurexe2x80x9d tends to be much less because the patient is supported by a greater area than on a conventional mattress, so the blood supply to the skin is much improved. This therapy is further improved by the technique of xe2x80x9calternating pressurexe2x80x9d, whereby the alternate air sacks of the mattress are inflated to a different pressure. The goal is to reduce the support pressure at half of the air sacks, while supporting the patient on the other half of the air sacks which are inflated. After a period of time, the configuration of deflated and inflated air sacks is switched, which means the patient is never supported at one place for an extended period of time. The alternating therapy allows for the skin that was under pressure to recover, have increased blood flow through the skin, and allows air to dry the skin, all of which helps to prevent skin ulcers.
There are many alternating air pressure systems on the market today. Many of these systems are very complex and expensive. Typically, one half of the air sacks are inflated by a blower. After a period of time, solenoid valves open to release the pressure and air is then blown into the other half of the air sacks with its solenoid valves shut. Again after a period of time, the solenoid valves open to release the pressure and the first half of the air sacks are reinflated.
The alternating pressure systems are typically complex and fairly expensive. What is needed therefore is an inexpensive simple alternating pressure system which alternates air in the different halves of the air sacks. What is also needed is an alternating pressure system that allows for alternating pressure while allowing for air flow in all the air sacks of the mattress.
The present invention accomplishes the objectives of alternating pressure by the use of a motor-driven rotor valve within a valve assembly.
The valve assembly as constructed has many important features. First, the valve is in the air discharge path from the blower, but prior to the mattress. Second, the valve has one inlet port to receive blower air, and two outlet ports to send the air on to the mattress through hoses. Third, the valve has a rotor with a wedge-shaped section that forms a type of shutter when positioned over a port leading to the mattress, thereby restricting the air flow through that port only. Fourth, the wedge feature can be positioned between the ports so as to restrict neither one, the mattress then being inflated to that same pressure over the entire surface. This mode is sometimes desired. Fifth, the rotor and wedge turn within a cylindrical cavity, but without touching the wall. Sixth, the rotor is supported by and rotated by a gearmotor shaft. Seventh, the rotor is positioned optically by means of light sensors. Eighth, the gearmotor is a DC motor and driven by a H-bridge circuit to allow reversing at the end of each cycle. Ninth, the cycle time in the preferred embodiment is about 3 minutes. And, tenth, the transit time (during which the rotor moves through about 120 degrees) is about 4 seconds.